InaugurationCast: Weather Gang & El Bombo Battle

Through January 13, CWG's chief and lead meteorologists -- Jason Samenow and Dan Stillman, respectively -- will provide dueling forecasts for Jan. 20, Inauguration Day. We'll also feature a reader prediction. Starting Jan. 14, we'll shift to a single CWG team forecast, in hopes of more confidently honing in on the forecast details.

For another day, Dan and I are standing firm with our initial inauguration weather predictions. Neither of us expect anything too extreme (on the hot or cold side), but both of us believe there's at least a slight chance of some precipitation. On the other hand, long-time Capital Weather Gang reader/commenter El Bombo (Bombo47jea) of DanceCast fame believes the region will get socked by a major storm. After a several month hiatus, he resumed posting on the blog yesterday.

Keep reading for Jason and Dan's initial predictions not to mention El Bombo's, and some inauguration weather history. And don't forget to comment with your own inauguration weather predictions.

Forecasting 18-days out is a bit of a crap shoot, but you can look at some of the large scale patterns and consider how they might evolve to help in developing a forecast. You can also review past years that featured similar weather patterns and examine what the weather was like around January 20th in those years. So I did all of that and drew the following conclusions:

*Chances are good there will be ridge of high pressure over the West coast of the U.S. that will cause most of our weather to come from Canada where it is cold.

*There probably won't be a strong blocking pattern over the Atlantic to hold cold air in place for long periods of time.

*There may be a ridge of high pressure off the Southeast coast that tries to steer some mild air towards our area.

Taking these factors together, I don't think it will be unusually cold or warm. I do think there will be a better than average chance of storminess either just before or sometime during Inauguration Day and precipitation could come in several types.

Let me start by saying how much I cringe at the misleading implication of forecasts beyond a week that us meteorologists can reliably predict a specific day's weather that far in advance. So you can only imagine how I feel about trying to forecast more than two weeks in advance. That said, I'm game for throwing my forecast out there with the rest of them, as long as we understand this is mostly just for fun until we get a lot closer to the event.

My forecast is based on several pieces of data I studied, a look at the weather in Januarys past, and a bit of gut instinct. With the Climate Prediction Center forecasting below-normal temperatures Jan. 9-15, I'm thinking that by the 20th we'll have veered in the other direction -- above normal. But I also don't see a January thaw happening that late in the month, so I won't go too much above normal.

As for precipitation, I'll start the bidding at a 30% chance of rain, with the threat of frozen precipitation staying north and west of D.C. I'm not gonna call for a big winter storm, mostly based on my hunch that an atmospheric index called the NAO may be in the positive range, after rising from negative toward neutral several days earlier.

Background: This is a historic inauguration, perhaps the most notable since that of JFK in 1961 (note: CWG will have an in-depth feature on this storm tomorrow), which as old hands know was marked by the sudden and unexpected snowstorm of Jan., 19, 1961.

Frankly, I wouldn't be surprised if a similar snowstorm were to hit us for the Obama inaugural in three weeks. Before that has to happen, though, the pattern has got to change.

If the pattern changes, look for a good snowstorm on Jan. 19th or 20th. If it doesn't and we stay in the same storm-track rut we've been in, look for a pretty good rainstorm, probably beginning as mixed precipitation, and possibly ending in the same manner.

Please note that we have a historic inaugural coming up, so we might have some "historic" weather. Don't look for anything as cold as the second Reagan inaugural in 1985.

Note: If you want your Inauguration forecast featured here in one of the coming days, summarize your prediction in a comment below.

Partly cloudy 43-46. Chance of accumulating snow between now & the 20th, 10%. Looking more & more like a rather snowless winter. I expect Feb temps to be above average, so we have about 31/2 weeks left 2 get a decent snow.

I've become a believer in the NAO, so if it's changing, things could be adverse to outdoor activity on the 20th. As to the NAO itself, I got a detailed reply on this before that was extremely informative, and I now know that the NAO cannot be calculated simply by looking at the barometric pressure readings in Reykjavik and Lisbon, but can a crude estimate be had that way? I'm just looking for an easy way to keep abreast of trends.

I personally think the period from about 1/10 through late January looks potentially more favorable for some light to moderate winter events. I'm far to gun-shy after recent years to call it probable, but things certainly look better than in past winters. Some very cold air looks to filter in during that period, the Pacific looks to get better, though the Atlantic will go bad on us.

Nonetheless, climatologically speaking, we are entering the "cold heart" of winter, and this is the small window where DC can in fact get some snow even in a less than ideal pattern. That, combined with a pattern that may feature some pretty deep cold (probably with a few mild days interspersed), suggests to me that we may have a window for precip to match up with cold air.